In relation to a supply of fuel to a gas turbine combustor, the fuel is sometimes supplied while being distributed into a plurality of systems, from the point of view of efficiency and stability of combustion. In such a case, the distribution of the fuel to each of the systems needs to be taken into account.
FIG. 21 is a diagram illustrating an example of fuel distribution control of a conventional gas turbine. As illustrated in FIG. 21, a conventional fuel control device estimates a temperature of combustion gas at a turbine inlet, on the basis of atmospheric pressure, atmospheric temperature, an inlet guide vane (IGV) opening designated value, and a gas turbine output value. The fuel control device calculates a ratio of the fuel to be allocated to each of the systems on the basis of the estimated turbine inlet temperature. The fuel control device determines a fuel supply amount to nozzles of each of the fuel systems on the basis of the distribution ratio to each of the systems, and a total fuel flow rate that is based on a fuel control signal command value (CSO). The fuel control device controls valve openings of fuel flow rate regulating valves provided in each of the systems, on the basis of that fuel supply amount.
Further, in the gas turbine combustor, when the distribution ratio of the fuel supplied from the plurality of systems is changed, for example, combustion oscillation is known to occur. The combustion oscillation is a pressure fluctuation inside the combustor, which causes damage to the combustor and gas turbine components. There is therefore a need to suppress the combustion oscillation (see Patent Document 1).
FIG. 22 is a diagram illustrating an example of relationships between fuel distribution ratios to fuel systems and a turbine inlet temperature at the time of a load change with conventional technology. As illustrated in the figure, depending on values of the fuel distribution ratios and the turbine inlet temperature, regions exist in which the combustion oscillation occurs (see reference sign 74 and reference sign 75). The reference sign 71 illustrates a target operation line representing a relationship between the fuel distribution ratio and the turbine inlet temperature at which this type of combustion oscillation does not occur. In the fuel control device, it is desirable to control the distribution ratio of the fuel supplied to each of the systems so as to obtain the fuel distribution ratio that can avoid the region in which the combustion oscillation occurs, as illustrated by the target operation line 71.